This invention relates generally to exercise devices and more particularly, to an ankle exercise device. There are numerous deficits affecting the ankle-foot complex, that is, the ability to use the ankle joint to move the foot with respect to the lower leg. For purposes of this application, the ankle-foot complex includes the skeletal structure of the ankle and foot and the surrounding muscle, nerves and tissues, or a portion of the ankle-foot complex; and the lower leg generally refers to the shank, that is, the portion of the leg between the knee and the ankle. Some deficits limit the range of motion of the foot with respect to the lower leg. Other deficits limit the strength of the muscles that move the foot. Such deficits may be congenital, acquired, orthopaedic, vascular or neurological. Such deficits may be caused by hemiplegia, paraplegia, quadriplegia, spinal cord injury, brain injury, CVA, diabetes, vascular problems, peripheral neuropathy, foot drop, fracture, contracture, heel cord repair, spinabifida, cerebral palsy, etc. Of particular interest, are those deficits which inhibit dorsiflexion, that is, the ability to pivot the foot with the ankle joint in an upward direction with respect to a horizontal axis passing through the ankle joint and plantarflexion, which is the ability to use the ankle joint to rotate the foot downward with respect to a generally horizontal axis passing through the ankle joint. For example, with one such deficit, which in the literature and this application is referred to as either "foot drop" or "drop foot", the motor control of dorsiflexion is impaired and may be completely inhibited. Thus, because of muscle or nerve damage, there is no ability to use the ankle-foot complex to lift the foot, and the foot hangs in a fully dropped position with respect to the lower leg.
There are exercise devices that may be used to provide physical therapy to improve deficits affecting the ankle. For example, some users can generally control the motion of their feet, but they may have deficits with respect to muscle strength and/or range of motion of the foot. There are exercise devices for such deficits which attach to the ball of the foot and provide a resistance to the user moving the foot in a dorsiflexion or plantarflexion motion. Further, the resistance to such motion is often variable so that muscle strength and range of motion may be restored. With other devices, the foot is resiliently held at the extreme of the dorsiflexion or plantarflexion position over extended periods of time, for example, overnight; and such devices assist the user in increasing the range of motion of the foot.
With other deficits, more complicated motorized foot articulators are known which reciprocate the foot through successive dorsiflexion and plantarflexion motions. Such motions may complement or resist muscular activity of the user. While all of the above described devices provide beneficial, therapeutic value, such devices are not beneficial or useful with respect to every deficit of the ankle-foot complex. For example, with a foot drop condition, one has no ability to move the foot; and thus, devices that are designed to provide a resistance to muscular activity cannot be used with a foot drop deficit. Further, motorized exercise devices for moving the foot are expensive, complicated, difficult to move and not readily used in a home environment.
Consequently, there is a need for an ankle exercise device that does not have the limitations and disadvantages of known ankle exercise devices.